Compressor unit for cryocooler and cryopump system

ABSTRACT

A compressor unit includes a flow control valve controlling a flow rate of a bypass pipe according to a valve command signal, a compressor inverter, and a controller. A range of operation frequency values is limited to a first operation frequency interval from a lower limit value to a first value and a second operation frequency interval from a second value to an upper limit value. When a target flow rate is between a first discharge flow rate and a second discharge flow rate, the controller generates an inverter command signal such that the operation frequency is set to the second operation frequency interval, and generates the valve command signal such that the flow rate of the bypass pipe coincides with a differential flow rate obtained by subtracting the target flow rate from a discharge flow rate of a compressor body obtained by the inverter command signal.

RELATED APPLICATIONS

The contents of Japanese Patent Application No. 2017-020625, and of International Patent Application No. PCT/JP2018/3571, on the basis of each of which priority benefits are claimed in an accompanying application data sheet, are in their entirety incorporated herein by reference.

BACKGROUND Technical Field

Certain embodiment of the present invention relates to a compressor unit for a cryocooler and a cryopump system.

Description of Related Art

In the related art, in a so-called inverter compressor mounted with an inverter and variable in an operation frequency, there is known a vibration suppression technology for changing the operation frequency of the compressor in a case where a detection output of a vibration sensor is large.

SUMMARY

According to an embodiment of the present invention, there is provided a compressor unit for a cryocooler. The compressor unit includes: a compressor structure portion which includes a compressor body configured to compress a working gas and discharge the working gas into the cryocooler, a compressor motor which has a variable operation frequency and is configured to operate the compressor body, a high-pressure pipe which is connected to the compressor body such that the working gas is discharged from the compressor body through the high-pressure pipe, a low-pressure pipe which is connected to the compressor body such that the working gas is sucked to the compressor body through the low-pressure pipe, a bypass pipe which bypasses the compressor body and connects the high-pressure pipe to the low-pressure pipe, which allows working gas to flow from the high-pressure pipe to the low-pressure pipe bypassing the compressor body, and a flow control valve which is provided in the bypass valve to control a flow rate of the bypass pipe according to a valve command signal; a compressor inverter configured to control an operation frequency of the compressor motor according to an inverter command signal; and a compressor controller configured to generate the valve command signal and the inverter command signal such that the working gas is supplied from the compressor unit to the cryocooler at a target flow rate. A range of operation frequency values is limited to a first operation frequency interval from a lower limit value larger than zero to a first value and a second operation frequency interval from a second value to an upper limit value, and the second value is larger than the first value. The first value and the second value are defined such that a frequency interval from the first value to the second value includes at least one natural frequency for at least a portion of the compressor structure portion. The lower limit value, the first value, the second value, and the upper limit value of the operation frequency correspond to a lower limit discharge flow rate, a first discharge flow rate, a second discharge flow rate, and an upper limit discharge flow rate of the compressor body, respectively. In a case where the target flow rate is between the first discharge flow rate and the second discharge flow rate, the compressor controller generates the inverter command signal such that the operation frequency is set to be in the second operation frequency interval, and generates the valve command signal such that the flow rate of the bypass pipe coincides with a differential flow rate obtained by subtracting the target flow rate from a discharge flow rate of the compressor body obtained according to the inverter command signal.

According to another embodiment of the present invention, there is provided a cryopump system including: a cryopump which includes a cryopanel and a cryocooler configured to cool the cryopanel; a compressor unit having a compressor structure portion including a compressor body configured to compress a working gas and discharge the working gas into the cryocooler, a compressor motor which has a variable operation frequency and is configured to operate the compressor body, a high-pressure pipe which is connected to the compressor body such that the working gas is discharged from the compressor body though the high-pressure pipe, a low-pressure pipe which is connected to the compressor body such that the working gas is sucked to the compressor body through the low-pressure pipe, a bypass pipe which bypasses the compressor body and connects the high-pressure pipe to the low-pressure pipe, which allows working gas to flow from the high-pressure pipe to the low-pressure pipe bypassing the compressor body, and a flow control valve which is provided in the bypass pipe to control a flow rate of the bypass pipe according to a valve command signal; a compressor inverter configured to control an operation frequency of the compressor motor according to an inverter command signal; and a controller configured to generate the valve command signal and the inverter command signal such that the working gas is supplied from the compressor unit to the cryocooler at a target flow rate. A range of operation frequency values is limited to a first operation frequency interval from a lower limit value larger than zero to a first value and a second operation frequency interval from a second value to an upper limit value, and the second value is larger than the first value. The first value and the second value are defined such that a frequency interval from the first value to the second value includes at least one natural frequency for at least a portion of the compressor structure portion. The lower limit value, the first value, the second value, and the upper limit value of the operation frequency correspond to a lower limit discharge flow rate, a first discharge flow rate, a second discharge flow rate, and an upper limit discharge flow rate of the compressor body, respectively. In a case where the target flow rate is between the first discharge flow rate and the second discharge flow rate, the controller generates the inverter command signal such that the operation frequency is set to be in the second operation frequency interval, and generates the valve command signal such that the flow rate of the bypass pipe coincides with a differential flow rate obtained by subtracting the target flow rate from a discharge flow rate of the compressor body obtained according to the inverter command signal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically showing an overall configuration of a cryopump system according to an embodiment of the present invention.

FIG. 2 is a sectional view schematically showing a cryopump according to the embodiment of the present invention.

FIG. 3 is a view schematically showing a compressor unit according to the embodiment of the present invention.

FIG. 4 is a control block diagram of a cryopump system according to the present embodiment.

FIG. 5 is a diagram for explaining a control flow of a compressor unit operation control according to the embodiment of the present invention.

FIG. 6 is a graph schematically showing an output distribution table according to the embodiment of the present invention.

DETAILED DESCRIPTION

It is desirable to provide a simple method to reduce vibrations in an inverter driven compressor unit for a cryocooler.

In addition, aspects of the present invention include arbitrary combinations of the above-described elements and mutual substitution of elements or expressions of the present invention among apparatuses, methods, systems, or the like.

According to the present invention, it is possible to reduce vibrations in an inverter driven compressor unit for a cryocooler by a simple method.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Moreover, in descriptions, the same elements will be denoted by the same reference signs, and repeated descriptions will be appropriately omitted. Further, configurations described below are examples and do not limit the scope of the present invention. In addition, in the drawings referred to in the following descriptions, a size and thickness of each component are for convenience of descriptions, and do not necessarily indicate an actual dimension and ratio.

A cryogenic system is known, which includes a cryocooler and a compressor unit for supplying a working gas to the cryocooler. As an example of the cryogenic system, a system including a cryogenic device (for example, a cryopump) which uses a cryocooler as a cooling source is also known. In the cryogenic system, for example, a pressure target value and the pressure measurement value are used to control an operation frequency of the compressor unit such that a differential pressure between a high pressure side and a low pressure side of the working gas of cryocooler coincides with a set value. A target flow rate of the working gas required for the cryocooler can be provided at an optimal (minimum) operation frequency, and thus, the control contributes to a reduction in power consumption of the system.

It is assumed that a natural frequency of a mechanical structure such as a pipe of the compressor unit is included in an operation frequency range used in an inverter. The compressor unit itself during an operation is a vibration source. As a value of the operation frequency approaches the natural frequency, resonance may occur in the mechanical structure of the compressor unit. Excessive vibrations, noises and, fatigues of structural members are not desired.

In order to avoid the problems, it is recommended to prohibit the operation frequency from having a value close to the natural frequency. However, this means that if the value of the optimal operation frequency is close to the natural frequency, instead of using the value, a value away from the natural frequency is used instead. If the operation frequency is changed to a smaller value, there is a concern that a supply flow rate from the compressor unit may be insufficient for a flow rate of the working gas required for the cryocooler. In a case where the operation frequency is changed to a larger value, the power consumption of the compressor unit increases, which leads to a disadvantage that the reduction in the power consumption of the inverter control cannot be sufficiently obtained.

As a fundamental solution, it is also conceivable to change design of the compressor unit such that the natural frequency of the mechanical structure is not included in the used operation frequency range. However, the design change takes time and effort.

According to an embodiment of the present invention, there is provided a compressor unit for a cryocooler. The compressor unit includes: a compressor structure portion which includes a compressor body configured to compress a working gas of the cryocooler and discharge the compressed working gas, a compressor motor which has a variable operation frequency and is configured to operate the compressor body, a high-pressure pipe which is connected to the compressor body such that the working gas is discharged from the compressor body, a low-pressure pipe which is connected to the compressor body such that the working gas is sucked to the compressor body, a bypass pipe which bypasses the compressor body and connects the high-pressure pipe to the low-pressure pipe, and a flow control valve which is provided in the bypass pipe to control a flow rate of the bypass pipe according to a valve command signal; a compressor inverter configured to control the operation frequency of the compressor motor according to an inverter command signal; and a compressor controller configured to determine the valve command signal and the inverter command signal such that the working gas is supplied from the compressor unit to the cryocooler at a target flow rate. A range of values which the operation frequency takes is preliminarily limited to a first operation frequency interval from a lower limit value larger than zero to a first value and a second operation frequency interval from a second value to an upper limit value, and the second value is larger than the first value. The first value and the second value are defined such that an unused frequency interval from the first value to the second value includes at least one natural frequency for at least a portion of the compressor structure portion. The lower limit value, the first value, the second value, and the upper limit value of the operation frequency correspond to a lower limit discharge flow rate, a first discharge flow rate, a second discharge flow rate, and an upper limit discharge flow rate of the compressor body, respectively. In a case where the target flow rate is between the first discharge flow rate and the second discharge flow rate, the compressor controller determines the inverter command signal such that the operation frequency is set to be in the second operation frequency interval, and determines the valve command signal such that the flow rate of the bypass pipe coincides with a differential flow rate obtained by subtracting the target flow rate from a discharge flow rate of the compressor body obtained according to the inverter command signal.

According to this aspect, the unused interval of the operation frequency is defined to include the natural frequency of the compressor structure portion, and thus, a resonance of the compressor structure portion caused by the operation of the compressor body is not easily generated. In addition, the inverter command signal is determined such that the operation frequency is set to be in the second operation frequency interval, and thus, the working gas is discharged from the compressor body to the high-pressure pipe at a total flow rate obtained by adding a surplus flow rate (the above-described differential flow rate) to the target flow rate. The valve command signal is determined such that the flow rate of the bypass pipe corresponds to the surplus flow rate, and thus, the working gas is collected from the high-pressure pipe to the low-pressure pipe, and the compressor unit can supply the working gas to the cryocooler at the target flow rate.

In the case where the target flow rate is between the first discharge flow rate and the second discharge flow rate, the compressor controller may determine the inverter command signal such that the operation frequency takes the second value.

In a case where the target flow rate is between the lower limit discharge flow rate and the first discharge flow rate, the compressor controller may determine the inverter command signal such that the operation frequency is set to be in the first operation frequency interval and may determine the valve command signal such that the flow control valve is closed. In a case where the target flow rate is between the second discharge flow rate and the upper limit discharge flow rate, the compressor controller may determine the inverter command signal such that the operation frequency is set to be in the second operation frequency interval and may determine the valve command signal such that the flow control valve is closed.

In a case where the target flow rate is between zero and the lower limit discharge flow rate, the compressor controller may determine the invert command signal such that the operation frequency takes the lower limit value and may determine the valve command signal such that the flow rate of the bypass pipe coincides with the differential flow rate.

The compressor controller may perform a smoothing process on the valve command signal and/or the inverter command signal when the operation frequency is switched from the first value to the second value.

FIG. 1 is a view schematically showing an overall configuration of a cryopump system 1000 according to an embodiment of the present invention. The cryopump system 1000 is used to evacuate a vacuum device 300. The vacuum device 300 is a vacuum processing device which processes an object under a vacuum environment, and is a device such as an ion implanter or a sputtering device used in a semiconductor manufacturing process, for example.

The cryopump system 1000 includes a plurality of cryopumps 10. The cryopumps 10 are attached to one or a plurality of vacuum chambers (not shown) of the vacuum device 300 and are used to increase a degree of vacuum inside the vacuum chamber to a level required for a desired process. The cryopump 10 is operated in accordance with a controlled variable determined by a cryopump controller (hereinafter, also referred to as a CP controller) 100. For example, a high degree of vacuum of about 10⁻⁵ Pa to 10⁻⁸ Pa is realized in the vacuum chamber. In the shown example, the cryopump system 1000 includes 11 cryopumps 10. The plurality of cryopumps 10 may be cryopumps having the same exhaust performance, or may be cryopumps having different exhaust performance.

The cryopump system 1000 includes the CP controller 100. The CP controller 100 controls the cryopumps 10 and compressor units 102 and 104. The CP controller 100 includes a CPU which executes various arithmetic processing, a ROM which stores various control programs, a RAM which is used as a work area for storing data and executing a program, an input/output interface, a memory, or the like. Moreover, the CP controller 100 is configured to be able to communicate with a host controller (not shown) for controlling the vacuum device 300. It can be said that the host controller of the vacuum device 300 is a high-level controller which controls each component of the vacuum device 300 including the cryopump system 1000.

The CP controller 100 is configured separately from the cryopumps 10 and the compressor units 102 and 104. The CP controller 100 is communicably connected to the cryopumps 10 and the compressor units 102 and 104. Each of the cryopumps 10 include an IO module 50 (refer to FIG. 4) for processing an input and output in communication with the CP controller 100. The CP controller 100 and each IO module 50 are connected by a control communication line. In FIG. 1, control communication lines between the cryopumps 10 and the CP controller 100 and control communication lines between the compressor units 102 and 104 and the CP controller 100 are shown by dashed line. Moreover, the CP controller 100 may be integrated with any of the cryopumps 10 or the compressor units 102 and 104.

The CP controller 100 may be constituted by a single controller or may include a plurality of controllers each performing the same or different functions. For example, the CP controller 100 may include a compressor controller which is provided in each compressor unit to determine a controlled variable of each compressor unit, and a cryopump controller which controls the cryopump system.

The cryopump system 1000 includes a plurality of compressor units at least including the first compressor unit 102 and the second compressor unit 104. The compressor unit is provided to circulate the working gas in a closed fluid circuit including the cryopump 10. The compressor unit collects the working gas from the cryopump 10, compresses the collected working gas, and feeds the compressed working gas back to the cryopump 10. The compressor unit is installed apart from the vacuum device 300 or in the vicinity of the vacuum device 300. The compressor unit is operated in accordance with a controlled variable determined by a compressor controller 168 (refer to FIG. 4). Alternatively, the compressor unit is operated in accordance with the controlled variable determined by the CP controller 100.

In the following, the cryopump system 1000 having two compressor units 102 and 104 will be described as a representative example. However, the present invention is not limited to this. Similarly to the compressor units 102 and 104, a cryopump system 1000 may be configured, in which three or more compressor units are connected in parallel to the plurality of cryopumps 10. In addition, the cryopump system 1000 shown in FIG. 1 includes the plurality of cryopumps 10 and the plurality of compressor units 102 and 104, respectively. However, the cryopump system 1000 may include one cryopump 10 or one of the compressor units 102 and 104.

The plurality of cryopumps 10 and the plurality of compressor units 102 and 104 are connected to each other by a working gas piping system 106. The piping system 106 is configured to connect the plurality of cryopumps 10 and the plurality of compressor units 102 and 104 in parallel to each other, and to allow the working gas to flow between the plurality of cryopumps 10 and the plurality of compressor units 102 and 104. Each of the plurality of compressor units is connected in parallel to one cryopump 10 by the piping system 106, and each of the plurality of cryopumps 10 is connected in parallel to one compressor unit.

The piping system 106 is configured to include an internal pipe 108 and an external pipe 110. The internal pipe 108 is formed inside the vacuum device 300 and includes an internal supply line 112 and an internal return line 114. The external pipe 110 is installed outside the vacuum device 300 and includes an external supply line 120 and an external return line 122. The external pipe 110 connects the vacuum device 300 and the plurality of compressor units 102 and 104 to each other.

The internal supply line 112 is connected to the gas supply port 42 of each cryopump 10 (refer to FIG. 2), and the internal return line 114 is connected to a gas discharge port 44 of each cryopump 10 (refer to FIG. 2). In addition, the internal supply line 112 is connected to one end of the external supply line 120 of the external pipe 110 at a gas supply port 116 of the vacuum device 300, and the internal return line 114 is connected to one end of the external return line 122 of the external pipe 110 at a gas exhaust port 118 of the vacuum device 300.

The outer end of the external supply line 120 is connected to a first manifold 124, and the other end of the external return line 122 is connected to a second manifold 126. One end of a first discharge pipe 128 of the first compressor unit 102 and one end of a second discharge pipe 130 of the second compressor unit 104 are connected to the first manifold 124. The other end of the first discharge pipe 128 and the other end of the second discharge pipe 130 are respectively connected to discharge ports 148 of the corresponding compressor units 102 and 104 (refer to FIG. 3). One end of a first suction pipe 132 of the first compressor unit 102 and one end of a second suction pipe 134 of the second compressor unit 104 are connected to the second manifold 126. The other end of the first suction pipe 132 and the other end of the second suction pipe 134 are respectively connected to suction ports 146 of the corresponding compressor units 102 and 104 (refer to FIG. 3).

In this manner, a common supply line for collecting the working gas fed from each of the plurality of compressor units 102 and 104 and supplying the collected working gas to the plurality of cryopumps 10 is constituted by the internal supply line 112 and the external supply line 120. In addition, a common return line for collecting the working gas discharged from the plurality of cryopumps 10 and returning the collected working gas to the plurality of compressor units 102 and 104 is constituted by the internal return line 114 and the external return line 122. In addition, each of the plurality of compressor units is connected to a common line through an individual pipe associated with each compressor unit. The manifold for joining the individual pipes is provided in a connection portion between the individual pipe and the common line. The first manifold 124 joins the individual pipes on the supply side, and the second manifold 126 joins the individual pipes on a collection side.

Depending on a layout of various devices in a place (for example, a semiconductor manufacturing plant) where the cryopump system 1000 is used, the above-described common line may have a corresponding length (unlike shown). By collecting the working gas in the common line, a total pipe length can be shorter than that in a case where each of the plurality of compressors is individually connected to the vacuum device. In addition, since there is the pipe configuration in which a plurality of compressors are connected for each supply target (for example, each cryopump 10 in the cryopump system 1000) of the working gas, redundancy may occur. The plurality of compressors are arranged in parallel to each target (for example, cryopump) so as to be operated, and thus, loads on the plurality of compressors are shared.

FIG. 2 is a sectional view schematically showing the cryopump 10 according to the embodiment of the present invention. The cryopump 10 includes a first cryopanel which is cooled to a first cooling temperature level and a second cryopanel which is cooled to a second cooling temperature level lower than the first cooling temperature level. In the first cryopanel, a gas having a low vapor pressure at the first cooling temperature level is trapped by condensation and is exhausted. For example, a gas (for example, 10⁻⁸ Pa) having a vapor pressure lower than that of a reference vapor pressure is exhausted. In the second cryopanel, a gas having a low vapor pressure at the second cooling temperature level is trapped by condensation and is exhausted. In the second cryopanel, an adsorption area is formed on a surface of the second cryopanel to trap a non-condensable gas which is not condensed even at a second cooling temperature level due to a high vapor pressure. For example, the adsorption area is formed by providing an adsorbent on a panel surface. The non-condensable gas is adsorbed and exhausted to the adsorption area cooled to the second cooling temperature level.

The cryopump 10 shown in FIG. 2 includes a cryocooler 12, a panel structure 14, and a heat shield 16. The cryocooler 12 generates chills by a thermal cycle which sucks the working gas, expands the working gas inside, and discharges the working gas. The panel structure 14 includes a plurality of cryopanels, which are cooled by the cryocooler 12. A cryogenic surface for trapping and exhausting a gas by condensation or adsorption is formed on the panel surface. Typically, an adsorbent such as activated carbon for adsorbing a gas is provided on the surface (for example, rear surface) of the cryopanel. The heat shield 16 is provided to protect the panel structure 14 from ambient radiant heat.

The cryopump 10 is a so-called vertical cryopump. The vertical cryopump is a cryopump in which the cryocooler 12 is inserted and disposed along an axial direction of the heat shield 16. In addition, the present invention can be similarly applied to so-called a horizontal cryopump. The horizontal cryopump is a cryopump in which a second stage cooling stage of the cryocooler is inserted and disposed in a direction (typically, orthogonal direction) intersecting the axial direction of the heat shield 16. In addition, the horizontal cryopump 10 is schematically shown in FIG. 1.

The cryocooler 12 is a so-called Gifford-McMahon cryocooler (so-called GM cryocooler). Moreover, the cryocooler 12 is a two-stage cryocooler, and includes a first stage cylinder 18, a second stage cylinder 20, a first cooling stage 22, a second cooling stage 24, and a cryocooler motor 26. The first stage cylinder 18 and the second stage cylinder 20 are connected in series to each other, and a first stage displacer and a second stage displacer (not shown) connected to each other are respectively built in the first stage cylinder 18 and the second stage cylinder 20. A regenerator material is incorporated inside the first stage displacer and the second stage displacer. In addition, the cryocooler 12 may be a cryocooler other than the two-stage GM cryocooler. For example, a single-stage GM cryocooler may be used, or a pulse tube cryocooler or a Solvay cryocooler may be used.

The cryocooler 12 includes a flow path switching mechanism which periodically switches a flow path of the working gas in order to periodically repeat suction and discharge of the working gas. For example, the flow path switching mechanism includes a valve unit and a drive unit which drives the valve unit. For example, the valve unit is a rotary valve and the drive unit is a motor for rotating the rotary valve. For example, the motor may be an AC motor or a DC motor. In addition, the flow path switching mechanism may be a direct acting mechanism driven by a linear motor.

The cryocooler motor 26 is provided on one end of the first stage cylinder 18. The cryocooler motor 26 is provided inside a motor housing 27 formed on an end portion of the first stage cylinder 18. The cryocooler motor 26 is connected to the first stage displacer and the second stage displacer such that the first stage displacer and the second stage displacer can reciprocate inside the first stage cylinder 18 and the second stage cylinder 20, respectively. Further, the cryocooler motor 26 is connected to a movable valve (not shown) provided inside the motor housing 27 such that the movable valve can rotate in forward and reverse directions.

The first cooling stage 22 is provided on an end portion of the first stage cylinder 18 on the second stage cylinder 20 side, that is, on a connection portion between the first stage cylinder 18 and the second stage cylinder 20. In addition, the second cooling stage 24 is provided on an end of the second stage cylinder 20. For example, the first cooling stage 22 and the second cooling stage 24 are fixed to the first stage cylinder 18 and the second stage cylinder 20 by brazing, respectively.

The cryocooler 12 is connected to the compressor unit 102 or 104 through the gas supply port 42 and the gas discharge port 44 provided outside the motor housing 27. The connection relationship between the cryopump 10 and the compressor units 102 and 104 is as described with reference to FIG. 1.

The cryocooler 12 internally expands a high-pressure working gas (for example, helium or the like) supplied from the compressor units 102 and 104 to generate chills in the first cooling stage 22 and the second cooling stage 24. The compressor units 102 and 104 collect the working gas expanded by the cryocooler 12, pressurize the working gas, and supply the working gas to the cryocooler 12.

Specifically, first, the high-pressure working gas is supplied from the compressor units 102 and 104 to the cryocooler 12. In this case, the cryocooler motor 26 drives a movable valve inside the motor housing 27 in a state where the gas supply port 42 and an internal space of the cryocooler 12 communicate with each other. If the internal space of the cryocooler 12 is filled with the high-pressure working gas, the movable valve is switched by the cryocooler motor 26 and the internal space of the cryocooler 12 communicates with the gas discharge port 44. Accordingly, the working gas is expanded and is collected in the compressor units 102 and 104. The first stage displacer and the second stage displacer respectively reciprocate inside the first stage cylinder 18 and the second stage cylinder 20 in synchronization with an operation of the movable valve. By repeating such a thermal cycle, the cryocooler 12 generates chills in the first cooling stage 22 and the second cooling stage 24.

The second cooling stage 24 is cooled to a temperature lower than that of the first cooling stage 22. For example, the second cooling stage 24 is cooled to about 10 K to 20 K, and the first cooling stage 22 is cooled to about 80 K to 100 K. A first temperature sensor 23 for measuring the temperature of the first cooling stage 22 is attached to the first cooling stage 22, and a second temperature sensor 25 for measuring the temperature of the second cooling stage 24 is attached to the second cooling stage 24.

The heat shield 16 is fixed to the first cooling stage 22 of the cryocooler 12 in a thermally connected state, and the panel structure 14 is fixed to the second cooling stage 24 of the cryocooler 12 in a thermally connected state. Therefore, the heat shield 16 is cooled to the same temperature as that of the first cooling stage 22, and the panel structure 14 is cooled to the same temperature as that of the second cooling stage 24. The heat shield 16 is formed in a cylindrical shape having an opening portion 31 on one end. The opening portion 31 is defined by an end portion inner surface of a cylindrical-side surface of the heat shield 16.

Meanwhile, a closed portion 28 is formed on a side of the heat shield 16 opposite to the opening portion 31, that is, on the other end on a pump bottom side. The closed portion 28 is formed by a flange portion which extends radially inward on an end portion on a pump bottom side of a cylindrical-side surface of the heat shield 16. The cryopump 10 shown in FIG. 2 is the vertical cryopump, and thus, the flange portion is attached to the first cooling stage 22 of the cryocooler 12. As a result, a columnar internal space 30 is formed inside the heat shield 16. The cryocooler 12 protrudes into the internal space 30 along a central axis of the heat shield 16, and the second cooling stage 24 is inserted into the internal space 30.

Moreover, in a case of the horizontal cryopump, typically, the closed portion 28 is completely closed. The cryocooler 12 is disposed so as to protrude from an opening portion for cryocooler attachment formed on a side surface of the heat shield 16 into the internal space 30 along a direction orthogonal to the central axis of the heat shield 16. The first cooling stage 22 of the cryocooler 12 is attached to the opening portion for cryocooler attachment of the heat shield 16 and the second cooling stage 24 of the cryocooler 12 is disposed in the internal space 30. The panel structure 14 is attached to the second cooling stage 24. Accordingly, the panel structure 14 is disposed in the internal space 30 of the heat shield 16. The panel structure 14 may be attached to the second cooling stage 24 via a panel attachment member having an appropriate shape.

In addition, a baffle 32 is provided in the opening portion 31 of the heat shield 16. The baffle 32 is provided to be separated from the panel structure 14 in a central axis direction of the heat shield 16. The baffle 32 is attached to an end portion of the heat shield 16 on the opening portion 31 side and is cooled to approximately the same temperature as that of the heat shield 16. When viewed from the vacuum chamber 80 side, for example, the baffles 32 may be formed concentrically or may be formed in other shapes such as a lattice shape. Moreover, a gate valve (not shown) is provided between the baffle 32 and the vacuum chamber 80. For example, the gate valve is closed when the cryopump 10 is operated, and is opened when the cryopump 10 evacuates the vacuum chamber 80. For example, the vacuum chamber 80 is provided in the vacuum device 300 shown in FIG. 1.

The heat shield 16, the baffle 32, the panel structure 14, and the first cooling stage 22 and the second cooling stage 24 of the cryocooler 12 are accommodated inside a pump case 34. The pump case 34 is formed by connecting two cylinders having different diameters to each other in series. In the pump case 34, a cylindrical-side end portion having a large diameter is opened, and a flange portion 36 for connecting the vacuum chamber 80 and the end portion to each other is formed to extend radially outward. In addition, in the pump case 34, a cylindrical-side end portion having a small diameter is fixed to the motor housing 27 of the cryocooler 12. The cryopump 10 is airtightly fixed to an exhaust opening of the vacuum chamber 80 through the flange portion 36 of the pump case 34, and thus, an airtight space integral with the internal space of the vacuum chamber 80 is formed. Each of the pump case 34 and the heat shield 16 is formed in a cylindrical shape and the pump case 34 and the heat shield 16 are coaxially disposed with each other. An inner diameter of the pump case 34 is slightly larger than an outer diameter of the heat shield 16, and thus, the heat shield 16 is disposed at a slight distance from an inner surface of the pump case 34.

When the cryopump 10 is operated, first, before the cryopump 10 is operated, the inside of the vacuum chamber 80 is roughed to about 1 Pa to 10 Pa using another suitable roughing pump. Thereafter, the cryopump 10 is operated. The first cooling stage 22 and the second cooling stage 24 are cooled by driving of the cryocooler 12, and the heat shield 16, the baffle 32, and the panel structure 14 which are thermally connected to the first cooling stage 22 and the second cooling stage 24 are also cooled.

The cooled baffle 32 cools gas molecules flying from the vacuum chamber 80 toward the inside of the cryopump 10, condenses a gas (such as water) whose vapor pressure is sufficiently low at the cooling temperature on a surface of the baffle 32, and exhausts the condensed gas. A gas whose vapor pressure is not sufficiently low at the cooling temperature of the baffle 32 passes through the baffle 32 and enters the inside of the heat shield 16. A gas (for example, argon or the like) whose vapor pressure becomes sufficiently low at a cooling temperature of the panel structure 14 out of the entering gas molecules is condensed on the surface of the panel structure 14 and exhausted. A gas (for example, hydrogen or the like) whose vapor pressure does not become sufficiently low even at the cooling temperature is attached to the surface of the panel structure 14, and is adsorbed by the cooled adsorbent and exhausted. In this way, in the cryopump 10, a degree of vacuum inside the vacuum chamber 80 can reach a desired level.

FIG. 3 is a view schematically showing the first compressor unit 102 according to the embodiment of the present invention. In the present embodiment, the second compressor unit 104 also has the same configuration as the first compressor unit 102. The compressor unit 102 is configured to include a compressor body 140 which increases a pressure of a gas, a low-pressure pipe 142 for supplying a low-pressure gas supplied from the outside to the compressor body 140, and a high-pressure pipe 144 for feeding a high-pressure gas compressed by the compressor body 140 to the outside.

As shown in FIG. 1, the low-pressure gas is supplied to the first compressor unit 102 through the first suction pipe 132. The first compressor unit 102 receives the return gas from the cryopump 10 at the suction port 146 and feeds the working gas to the low-pressure pipe 142. The suction port 146 is provided in a compressor housing 138 of the first compressor unit 102 at the end of the low-pressure pipe 142. The low-pressure pipe 142 connects the suction port 146 and a suction port of the compressor body 140.

The low-pressure pipe 142 includes a storage tank 150 as a volume for removing a pulsation contained in the return gas. The storage tank 150 is provided between the suction port 146 and a branch to a bypass mechanism 152 described later. The working gas whose pulsation is removed in the storage tank 150 is supplied to the compressor body 140 through the low-pressure pipe 142. Inside the storage tank 150, a filter may be provided to remove unnecessary particles or the like from the gas. A receiving port and a pipe for replenishing the working gas from the outside may be connected to a portion between the storage tank 150 and the suction port 146.

For example, the compressor body 140 is a scroll type pump or a rotary type pump, and has a function which increases a pressure of the suctioned gas. A compressor motor 172 is provided in the compressor body 140, and the compressor body 140 is driven by the compressor motor 172. The compressor body 140 sends the working gas whose pressure has increased to the high-pressure pipe 144. The compressor body 140 is configured to perform cooling using oil, and an oil cooling pipe through which the oil circulates is provided along with the compressor body 140. Accordingly, the working gas whose pressure has increased is fed to the high-pressure pipe 144 in a state where the oil is slightly mixed with the working gas.

Therefore, an oil separator 154 in a middle of the high-pressure pipe 144. The oil separated from the working gas at the oil separator 154 may be returned to the low-pressure pipe 142 and may be returned to the compressor body 140 through the low-pressure pipe 142. The oil separator 154 may include a relief valve for releasing an excessively high pressure.

A heat exchanger for cooling the high-pressure working gas fed out from the compressor body 140 may be provided in a middle of the high-pressure pipe 144 which connects the compressor body 140 and the oil separator 154 to each other (not shown). For example, the heat exchanger cools the working gas by cooling water. Moreover, this cooling water may also be used so as to cool the oil which cools the compressor body 140. A temperature sensor for measuring the temperature of the working gas may be provided in the high-pressure pipe 144 at least one of an upstream side and a downstream side of the heat exchanger.

The working gas which has passed through the oil separator 154 is fed to an adsorber 156 through the high-pressure pipe 144. For example, the adsorber 156 is provided to remove, from the working gas, contaminating components which are not removed by a filter in the storage tank 150 or contaminant removal means on a flow path of the oil separator 154 or the like. For example, the adsorber 156 removes a vaporized oil component by means of adsorbing.

The discharge port 148 is provided in the compressor housing 138 of the first compressor unit 102 at the end of the high-pressure pipe 144. That is, the high-pressure pipe 144 connects the compressor body 140 and the discharge port 148 to each other, and the oil separator 154 and the adsorber 156 are provided halfway between them. The working gas via the adsorber 156 is fed to the cryopump 10 through the discharge port 148.

The first compressor unit 102 comprises a bypass mechanism 152 having a bypass pipe 158 which connects the low-pressure pipe 142 and the high-pressure pipe 144 to each other. In the shown embodiment, the bypass pipe 158 branches off from the low-pressure pipe 142 between the storage tank 150 and the compressor body 140. In addition, the bypass pipe 158 branches off from the high-pressure pipe 144 between the oil separator 154 and the adsorber 156.

The bypass mechanism 152 includes a control valve for controlling a flow rate of the working gas which bypasses from the high-pressure pipe 144 to the low-pressure pipe 142 without being fed to the cryopump 10. In the shown embodiment, a first control valve (also referred to as a pressure equalizing valve) 160 and a second control valve (also referred to as a relief valve) 162 are provided in parallel in a middle of the bypass pipe 158. For example, the pressure equalizing valve 160 is a normally open solenoid valve. Therefore, if the operation of the first compressor unit 102 is stopped (that is, if a power supply to the first compressor unit 102 is stopped), the pressure equalizing valve 160 is opened and the pressures of the low-pressure pipe 142 and the high-pressure pipe 144 are equal to each other. For example, the relief valve 162 is a normally closed solenoid valve. In the present embodiment, the relief valve 162 is used as a flow control valve of the bypass pipe 158 while the first compressor unit 102 is operated.

The first compressor unit 102 includes a first pressure sensor 164 for measuring a pressure of a gas returned from the cryopump 10 and a second pressure sensor 166 for measuring a pressure of a gas fed to the cryopump 10. The pressure of the fed gas is higher than the pressure of the return gas while the first compressor unit 102 is operated, and thus, hereinafter, the first pressure sensor 164 and the second pressure sensor 166 may be referred to as a low-pressure sensor and a high-pressure sensor, respectively.

The first pressure sensor 164 is provided to measure a pressure of the low-pressure pipe 142, and the second pressure sensor 166 is provided to measure a pressure of the high-pressure pipe 144. For example, the first pressure sensor 164 is installed in the storage tank 150, and measures the pressure of the return gas whose pulsation is removed in the storage tank 150. The first pressure sensor 164 may be provided at any position of the low-pressure pipe 142. The second pressure sensor 166 is provided between the oil separator 154 and the adsorber 156. The second pressure sensor 166 may be provided at any position of the high-pressure pipe 144.

Moreover, the first pressure sensor 164 and the second pressure sensor 166 may be provided outside the first compressor unit 102, and may be provided in the first suction pipe 132 and the first discharge pipe 128, for example. Further, the bypass mechanism 152 may also be provided outside the first compressor unit 102. For example, the first suction pipe 132 and the first discharge pipe 128 may be connected to each other by the bypass pipe 158.

The compressor structure portion 136 shown in FIG. 3 includes the compressor body 140, the low-pressure pipe 142, the high-pressure pipe 144, the suction port 146, the discharge port 148, the storage tank 150, the bypass mechanism 152, the oil separator 154, the adsorber 156, the bypass pipe 158, the pressure equalizing valve 160, the relief valve 162, the first pressure sensor 164, the second pressure sensor 166, and the compressor motor 172. These components are contained in the compressor housing 138.

FIG. 4 is a control block diagram of the cryopump system 1000 according to the present embodiment. FIG. 4 shows main portions of the cryopump system 1000 according to the embodiment of the present invention. Internal details of one of the plurality of cryopumps 10 will be shown, and the other cryopumps 10 will be omitted because they are similar. Similarly, the first compressor unit 102 will be described in detail, and the second compressor unit 104 is similar to that, and thus, the internal illustration will be omitted.

As described above, the CP controller 100 is communicably connected to an IO module 50 of each cryopump 10. The IO module 50 includes a cryocooler inverter 52 and a signal processing unit 54. The cryocooler inverter 52 regulates power having a prescribed voltage and frequency supplied from an external power source such as a commercial power source and supplies the power to the cryocooler motor 26. The voltage and frequency to be supplied to the cryocooler motor 26 are controlled by the CP controller 100.

The CP controller 100 determines a command controlled variable based on a sensor output signal. The signal processing unit 54 relays the command controlled variable transmitted from the CP controller 100 to the cryocooler inverter 52. For example, the signal processing unit 54 converts a command signal from the CP controller 100 into a signal which can be processed by the cryocooler inverter 52 and sends the converted signal to the cryocooler inverter 52. The command signal includes a signal representing an operation frequency of the cryocooler motor 26. Further, the signal processing unit 54 relays outputs of various sensors of the cryopump 10 to the CP controller 100. For example, the signal processing unit 54 converts the sensor output signal into a signal which can be processed by the CP controller 100 and transmits the converted signal to the CP controller 100.

Various sensors including the first temperature sensor 23 and the second temperature sensor 25 are connected to the signal processing unit 54 of the IO module 50. As described above, the first temperature sensor 23 measures the temperature of the first cooling stage 22 of the cryocooler 12 and the second temperature sensor 25 measures the temperature of the second cooling stage 24 of the cryocooler 12. The first temperature sensor 23 and the second temperature sensor 25 periodically measure the temperatures of the first cooling stage 22 and the second cooling stage 24, respectively, and output a signal indicating the measured temperature. Measured values of the first temperature sensor 23 and the second temperature sensor 25 are input to the CP controller 100 at predetermined time intervals and stored and held in a predetermined storage area of the CP controller 100.

The CP controller 100 controls the cryocooler 12 based on a temperature of the cryopanel. The CP controller 100 gives a command signal to the cryocooler 12 such that an actual temperature of the cryopanel follows a target temperature. For example, the CP controller 100 generates a cryocooler inverter command signal by a feedback control so as to minimize a deviation between a target temperature of a first stage cryopanel and a measured temperature of the first temperature sensor 23. The cryocooler inverter command signal is applied from the CP controller 100 to the cryocooler inverter 52 via the IO module 50. The cryocooler inverter 52 controls the operation frequency of the cryocooler motor 26 in accordance with the cryocooler inverter command signal. A rotational frequency of the cryocooler motor 26, that is, a frequency of the thermal cycle of the cryocooler 12 is determined according to the operation frequency of the cryocooler motor 26. For example, a target temperature of the first stage cryopanel is set as a specification according to the process performed in the vacuum chamber 80. In this case, the second cooling stage 24 and the panel structure 14 of the cryocooler 12 are cooled to a temperature determined by the specification of the cryocooler 12 and a heat load from the outside.

In a case where the measured temperature of the first temperature sensor 23 is higher than the target temperature, the CP controller 100 outputs a cryocooler inverter command signal to the IO module 50 to increase the operation frequency of the cryocooler motor 26. The frequency of the thermal cycle in the cryocooler 12 also increases in conjunction with an increase in the motor operation frequency, and the first cooling stage 22 of the cryocooler 12 is cooled toward the target temperature. Conversely, in a case where the measured temperature of the first temperature sensor 23 is lower than the target temperature, the operation frequency of the cryocooler motor 26 decreases and the temperature of the first cooling stage 22 of the cryocooler 12 increases toward the target temperature.

Normally, the target temperature of the first cooling stage 22 is set to a constant value. Accordingly, the CP controller 100 outputs the cryocooler inverter command signal so as to increase the operation frequency of the cryocooler motor 26 when the thermal load to the cryopump 10 increases, and outputs the cryocooler inverter command signal so as to decrease the operation frequency of the cryocooler motor 26 when the thermal load to the cryopump 10 decreases. Moreover, the target temperature may be changed appropriately, and for example, the target temperature of the cryopanel may be set sequentially so as to realize a target atmospheric pressure in an exhaust target volume. In addition, the CP controller 100 may control the operation frequency of the cryocooler motor 26 such that an actual temperature of the second stage cryopanel coincides with the target temperature.

In a typical cryopump, the frequency of the thermal cycle is always constant. It is set to operate at a relatively large frequency so as to enable rapid cooling from the room temperature to a pump operating temperature, and in case where the thermal load from the outside is small, the temperature of the cryopanel is adjusted by heating with a heater. Accordingly, power consumption increases. Meanwhile, in the present embodiment, since the thermal cycle frequency is controlled according to the thermal load to the cryopump 10, the cryopump having excellent energy saving properties can be realized. In addition, elimination of the necessity of providing a heater also contributes to a reduction of the power consumption.

The CP controller 100 is communicably connected to the compressor controller 168. A control unit of the cryopump system 1000 according to the embodiment of the present invention is constituted by a plurality of controllers including the CP controller 100 and the compressor controller 168. In another embodiment, a control unit of the cryopump system 1000 may be constituted by a single CP controller 100, and the compressor units 102 and 104 may be provided with an IO module instead of the compressor controller 168. In this case, the IO module relays a control signal between the CP controller 100 and each component of the compressor units 102 and 104. In addition, the compressor controller 168 may form a portion of the CP controller 100.

The compressor controller 168 controls the first compressor unit 102 based on a control signal from the CP controller 100 or independently of the CP controller 100. In one embodiment, the compressor controller 168 receives signals representing various set values from the CP controller 100 and controls the first compressor unit 102 using the set values. The compressor controller 168 determines the command controlled variable based on the sensor output signal. Similarly to the CP controller 100, the compressor controller 168 includes a CPU which executes various arithmetic processing, a ROM which stores various control programs, a RAM which is used as a work area for storing data and executing a program, an input/output interface, a memory, or the like.

In addition, the compressor controller 168 transmits a signal representing an operating condition of the first compressor unit 102 to the CP controller 100. For example, the signal indicating the operating state includes measured pressures of the first pressure sensor 164 and the second pressure sensor 166, an opening degree or control current of the relief valve 162, the operation frequency of the compressor motor 172, or the like.

The first compressor unit 102 includes a compressor inverter 170 and the compressor motor 172. The compressor motor 172 is a motor which operates the compressor body 140 and has a variable operation frequency, and is provided in the compressor body 140. Similarly to the cryocooler motor 26, various motors can be employed as the compressor motor 172. The compressor controller 168 generates a compressor inverter command signal and outputs the compressor inverter command signal to the compressor inverter 170. The compressor inverter 170 controls the operation frequency of the compressor motor 172 according to the compressor inverter command signal. The rotational frequency of the compressor motor 53 is controlled in accordance with the operation frequency of the compressor motor 172. The compressor inverter 170 regulates power having a prescribed voltage and frequency supplied from an external power source such as a commercial power source according to the compressor inverter command signal and supplies the power to the compressor motor 172. The voltage and frequency to be supplied to the compressor motor 172 are determined by the compressor inverter command signal.

Various sensors including the first pressure sensor 164 and the second pressure sensor 166 are connected to the compressor controller 168. As described above, the first pressure sensor 164 periodically measures a suction-side pressure of the compressor body 140, and the second pressure sensor 166 periodically measures a discharge-side pressure of the compressor body 140. The measured values of the first pressure sensor 164 and the second pressure sensor 166 are input to the compressor controller 168 at predetermined time intervals and stored and held in a predetermined storage area of the compressor controller 168.

The above-mentioned relief valve 162 is connected to the compressor controller 168. A relief valve driver 174 for driving the relief valve 162 is provided along with the relief valve 162, and the relief valve driver 174 is connected to the compressor controller 168. The compressor controller 168 generates a relief valve command signal and outputs the relief valve command signal to the relief valve driver 174. The relief valve command signal determines an opening degree of the relief valve 162, and the relief valve driver 174 controls the relief valve 162 to the opening degree. In this way, the relief valve 162 is provided in the bypass pipe 158 so as to control a flow rate of the bypass pipe 158 in accordance with the relief valve command signal. The relief valve driver 174 maybe incorporated in the compressor controller 168.

The compressor controller 168 controls the compressor body 140 to maintain a differential pressure (hereinafter, also referred to as a compressor differential pressure) between an inlet and an outlet of the compressor unit 102 at a target differential pressure. For example, the compressor controller 168 performs a feedback control such that the differential pressure between the inlet and outlet of the compressor unit 102 is a constant value. In one embodiment, the compressor controller 168 determines the compressor differential pressure from the measured values of the first pressure sensor 164 and the second pressure sensor 166. The compressor controller 168 determines the operation frequency of the compressor motor 172 such that the compressor differential pressure coincides with the target value. The compressor controller 168 controls the compressor inverter 170 to realize the operation frequency thereof. In addition, the target value of differential pressure may be changed while a differential pressure constant control is performed.

A further reduction in the power consumption is realized by the differential pressure constant control. In a case where the thermal load to the cryopump 10 and the cryocooler 12 is small, the thermal cycle frequency in the cryocooler 12 decreases due to the above-described cryopanel temperature control. Then, an amount of working gas required for the cryocooler 12 is reduced. In this case, an amount of gas exceeding a required amount may be fed from the compressor unit 102. Therefore, the differential pressure between the inlet and outlet of the compressor unit 102 tries to increase. However, in the present embodiment, the operation frequency of the compressor motor 172 is controlled so as to cause the compressor differential pressure to be constant. In this case, if the differential pressure is reduced to the target value, the operation frequency of the compressor motor 172 decreases. Therefore, the power consumption can be reduced as compared with a case where the compressor is operated at a constant operation frequency as in a typical cryopump.

Meanwhile, when the thermal load to the cryopump 10 increases, the operation frequency of the compressor motor 172 increases to cause the compressor differential pressure to be constant. Accordingly, since the amount of gas supplied to the cryocooler 12 can be sufficiently secured, a deviation of the cryopanel temperature from the target temperature due to an increase in the thermal load can be minimized.

In particular, when a timing at which the valve opens on the high pressure side for sucking the working gas overlaps or approaches the cryocoolers 12, a total amount of required gas increases. For example, if the compressor is simply operated at a constant discharge flow rate, or if a discharge pressure of the compressor is insufficient, an amount of gas supplied is smaller for a cryocooler which opens the valve later than a cryocooler which opens the valve first and then sucks the gas. The difference in the amount of supplied gas among the plurality of cryocoolers 12 causes a variation in refrigeration capacity among the cryocoolers 12. As compared with this case, by performing the differential pressure control, the flow rate of the working gas to the cryocooler 12 can be sufficiently secured. The differential pressure control not only contributes to energy saving, but also can suppress the variation in the refrigeration capacity among the plurality of cryocoolers 12.

FIG. 5 is a diagram for explaining a control flow of a compressor unit operation control according to the embodiment of the present invention. Control processing shown in FIG. 5 is repeatedly performed by the compressor controller 168 at predetermined intervals during operation of the cryopump 10. This processing is performed independently of the other compressor units 102 and 104 in the compressor controller 168 of each of the compressor units 102 and 104. In FIG. 5, a portion showing the arithmetic processing in the compressor controller 168 is divided by dashed lines, and a portion showing the operation of the hardware of the compressor units 102 and 104 is divided by dashed dotted lines.

The compressor controller 168 includes a controlled variable calculation unit 176. For example, the controlled variable calculation unit 176 is configured to calculate a command controlled variable for at least a differential pressure constant control. In this embodiment, the calculated command controlled variable is distributed to the operation frequency of the compressor motor 172 and the opening degree of the relief valve 162 to execute the differential pressure constant control. In another embodiment, the differential pressure constant control may be executed with only one of the operation frequency of the compressor motor 172 and the opening degree of the relief valve 162 as the command controlled variable. As described later, the controlled variable calculation unit 176 may be configured to calculate a command controlled variable for at least one of the differential pressure constant control, a discharge pressure control, and/or a suction pressure control.

As shown in FIG. 5, a target differential pressure ΔP₀ is preset and input to the compressor controller 168. For example, the target differential pressure is set by the CP controller 100 and is applied to the compressor controller 168. A suction-side measurement pressure PL is measured by the first pressure sensor 164 and a discharge-side measurement pressure PH is measured by the second pressure sensor 166, and the measurement pressures PL and PH are applied from the respective sensors to the compressor controller 168. In general, the measurement pressure PL of the first pressure sensor 164 is lower than the measurement pressure PH of the second pressure sensor 166.

The compressor controller 168 includes a deviation calculation unit 178 which obtains a measurement differential pressure ΔP by subtracting the suction-side measurement pressure PL from the discharge-side measurement pressure PH, and obtains a differential pressure deviation e by subtracting the measurement differential pressure ΔP from a set differential pressure ΔP0. For example, the controlled variable calculation unit 176 of the compressor controller 168 calculates a command controlled variable D from the differential pressure deviation e by predetermined controlled variable arithmetic processing including a PD operation or a PID operation.

In addition, as shown in FIG. 5, the compressor controller 168 may include the deviation calculation unit 178 separately from the controlled variable calculation unit 176, or the controlled variable calculation unit 176 may include the deviation calculation unit 178. Moreover, an integration operation unit for integrating the command controlled variable D for a predetermined time and applying the integrated command controlled variable to an output distribution processing unit 180 may be provided in a rear stage of the controlled variable calculation unit 176.

The compressor controller 168 includes the output distribution processing unit 180 which distributes the command controlled variable D to a first output command value D1 and a second output command value D2. The output distribution processing unit 180 determines the first output command value D1 and the second output command value D2 in accordance with the value of the command controlled variable D. The output distribution processing unit 180 refers to the output distribution table 181 and determines the first output command value D1 and the second output command value D2 from the command controlled variable D according to the output distribution table 181. The output distribution table 181 is prepared in advance and held in the output distribution processing unit 180 or the compressor controller 168.

The command controlled variable D is a parameter corresponding to a target flow rate of the compressor unit. The command controlled variable D represents a flow rate of the working gas which should be fed by the compressor unit so as to realize the target pressure such as the target differential pressure ΔP₀. In addition, the command controlled variable D does not have to directly represent the target flow rate itself of the compressor unit. The command controlled variable D may be a parameter associated with the target flow rate of the compressor unit by a function or a table, or any parameter correlated with the target flow rate of the compressor unit.

The first output command value D1 is a parameter corresponding to an operation frequency command value of the compressor motor 172. The first output command value D1 may be a parameter associated with the operation frequency command value by a function or a table, or any parameter correlated with the operation frequency command value. The second output command value D2 is a parameter corresponding to an opening degree command value of the relief valve 162. The second output command value D2 may be a parameter associated with the opening command value by a function or a table, or any parameter correlated with the opening command value.

The compressor controller 168 includes an inverter command unit 182 which generates a compressor inverter command signal E from the first output command value D1, and a relief valve command unit 184 which generates a relief valve command signal R from the second output command value D2. The compressor inverter command signal E is applied to the compressor inverter 170, and the operation frequency of the compressor body 140, that is, the compressor motor 172 is controlled in accordance with the instruction. For example, the compressor inverter command signal E is a voltage signal or other electrical signals representing the operation frequency command value. Further, the relief valve command signal R is applied to the relief valve driver 174, and an opening degree of the relief valve 162 is controlled in accordance with the instruction. The relief valve command signal R is an electrical signal which represents the opening degree command value of the relief valve 162, and is a pulse output signal for driving a solenoid coil, for example.

In this way, the compressor controller 168 determines the relief valve command signal R and the compressor inverter command signal E such that working gas is supplied from the compressor units 102 and 104 to the cryopump 10 (that is, cryocooler 12) at the target flow rate. The compressor controller 168 controls the opening degree of the relief valve 162 based on the determined relief valve command signal R. The compressor controller 168 outputs the relief valve command signal R to the relief valve driver 174, and thus, the relief valve 162 is opened according to the relief valve command signal R. In addition, the compressor controller 168 controls the operation frequency of the compressor body 140 based on the determined compressor inverter command signal E. The compressor controller 168 outputs the compressor inverter command signal E to the compressor inverter 170, and thus, the operation frequency of the compressor motor 172 is controlled according to the compressor inverter command signal E.

The pressure of the helium which is the working gas is determined by operating conditions of the compressor body 140 and the relief valve 162, and characteristics of associated pipes, tanks, or the like. The helium pressure determined in this way is measured by the first pressure sensor 164 and the second pressure sensor 166.

As described above, in each of the compressor units 102 and 104, the differential pressure constant control is performed independently by each of the compressor controllers 168. The compressor controller 168 performs a feedback control to minimize (preferably, zero) the differential pressure deviation e.

However, the deviation e shown in FIG. 5 is not limited to the deviation of the differential pressure. In an embodiment, the compressor controller 168 may perform a discharge pressure control which calculates a command controlled variable from a deviation between the discharge-side measurement pressure PH and a set pressure. In this case, the set pressure may be an upper limit value of a discharge-side pressure of the compressor. The compressor controller 168 may calculate the command controlled variable from the deviation between the discharge-side measurement pressure PH and the upper limit value when the discharge-side measurement pressure PH exceeds the upper limit value. For example, the upper limit value may be set empirically or experimentally as appropriate based on a maximum discharge pressure of the compressor which guarantees an exhaust capacity of the cryopump 10.

In this way, it is possible to suppress an excessive increase in the discharge pressure and to further enhance the safety. Accordingly, the discharge pressure control is an example of a protection control for the compressor unit.

Further, in an embodiment, the compressor controller 168 may perform a suction pressure control which calculates the command controlled variable from a deviation between the suction-side the measurement pressure PL and a set pressure. In this case, the set pressure may be a lower limit value of a suction-side pressure of the compressor. The compressor controller 168 may calculate the command controlled variable from the deviation between the suction-side measurement pressure PL and the lower limit value when the suction-side measurement pressure PL is lower than the lower limit value. For example, the lower limit value may be set empirically or experimentally as appropriate based on a minimum suction pressure of the compressor which guarantees the exhaust capacity of the cryopump 10.

In this way, it is possible to suppress an excessive temperature increase of the compressor body caused by a decrease in the working gas flow rate accompanying a decrease in the suction pressure. In addition, it is possible to continue the operation for a period of time while preventing an excessive pressure drop without immediately stopping operation when there is a gas leak from the piping system of the working gas. Accordingly, the suction pressure control is an example of the protection control for the compressor unit.

FIG. 6 is a graph schematically showing the output distribution table 181 according to the embodiment of the present invention. A vertical axis represents the first output command value D1 (solid lines) and the second output command value D2 (dashed lines), and a horizontal axis represents the command controlled variable D. The first output command value D1 is indicated by the solid lines, and the second output command value D2 is indicated by the broken lines. As described above, the first output command value D1 and the second output command value D2 correspond to or correlate with the operation frequency command value and the opening degree command value, respectively, and the command controlled variable D corresponds to or correlates with the target flow rate of the compressor unit. Accordingly, the output distribution table 181 represents a relationship between the operation frequency command value of the compressor motor 172 and the target flow rate of the compressor unit, and a relationship between the opening degree command value of the relief valve 162 and the target flow rate of the compressor unit.

A range of values which the first output command value D1 takes is preliminarily limited to a first interval and a second interval. The first interval is in a range from a lower limit value D1L to a first value D11, and the second interval is in a range from a second value D12 to an upper limit value D1U. Since the first output command value D1 is correlated with the operation frequency command value, the lower limit value D1L, the first value D11, the second value D12, and the upper limit value D1U shown correspond to the lower limit value, the first value, the second value, the upper limit value of the operation frequency, respectively.

Therefore, according to the output distribution table 181, the range of the values which the operation frequency takes is preliminarily limited to a first operation frequency interval from the lower limit value to the first value, and a second operation frequency interval from the second value to the upper limit value. The lower limit value of the operation frequency may be greater than zero. For example, the lower limit value may be between 20 Hz and 40 Hz or between 25 Hz and 35 Hz, and may be 30 Hz, for example. For example, the upper limit value of the operation frequency is between 70 Hz and 90 Hz or 75 Hz and 85 Hz, and may be 78 Hz, for example. For example, the upper limit value and the lower limit value of the operation frequency are predetermined as specifications of the compressor.

An interval from the first value D11 to the second value D12 is not used. An unused frequency interval from the first value to the second value of the operation frequency corresponding to this interval is defined to include at least one natural frequency ω0 for at least a portion (for example, the pipe such as the low-pressure pipe 142, the high-pressure pipe 144, or the bypass pipe 158) of the compressor structure portion 136. The first value and the second value of the operation frequency are between the lower limit value and the upper limit value, and the second value is larger than the first value. Natural frequency ω0 is known by an empirical knowledge, an experiment, or a simulation of a designer. The first value is set to a value smaller than the natural frequency ω0, and the second value is set to a value larger than the natural frequency ω0.

In the output distribution table 181, a first value d1, a second value d2, a third value d3, and a fourth value d4 of the command controlled variable D are associated with the lower limit value D1L, the first value D11, the second value D12, and the upper limit value D1U of the first output command value D1. Between sets (that is, (d1, D1L), (d2, D11), (d3, D12), (d4, D1U)) of the command controlled variable D and the first output command value D1 designated in this way is linearly interpolated, the relationship between the command controlled variable D and the first output command value D1 is defined by a linear interpolation.

As shown in FIG. 6, in a case where the command controlled variable D is between a minimum value d0 and the first value d1, the first output command value D1 takes the lower limit value D1L. In a case where the command controlled variable D is between the first value d1 and the second value d2, the first output command value D1 is between the lower limit value D1 L and the first value D11, and the first output command value D1 has a linear or proportional relationship with the command controlled variable D. If the command controlled variable D is between the second value d2 and the third value d3, the first output command value D1 takes the second value D12. In a case where the command controlled variable D is between the third value d3 and the fourth value d4, the first output command value D1 is between the second value D12 and the upper limit value D1U, and the first output command value D1 has a linear or proportional relationship with the command controlled variable D.

According to the relationship between the command controlled variable D and the first output command value D1, in the output distribution table 181, the lower limit discharge flow rate, the first discharge flow rate, the second discharge flow rate, and the upper limit discharge flow rate of the compressor body 140 are associated with the lower limit value, the first value, the second value, and the upper limit value of the operation frequency. Ina case where the target flow rate of the compressor unit is smaller than the lower limit discharge flow rate, the operation frequency is fixed to the lower limit value. When the target flow rate increases from the lower limit discharge flow rate to the first discharge flow rate, the operation frequency increases linearly from the lower limit value to the first value. If the target flow rate reaches the first discharge flow rate, the operation frequency is switched from the first value to the second value and increases discontinuously. When the target flow rate increases from the first discharge flow rate to the second discharge flow rate, the operation frequency is fixed to the second value. When the target flow rate increases from the second discharge flow rate to the upper limit value, the operation frequency increases linearly from the second value to the upper limit value. When the target flow rate decreases, the operation frequency is changed in the opposite manner.

In addition, in the output distribution table 181, the minimum value d0, the first value d1, the second value d2, the third value d3, and the fourth value d4 of the command controlled variable D are associated with a maximum value D22, a minimum value D20, an intermediate value D21, a minimum value D20, and a minimum value D20 of the second output command value D2. The maximum value D22 of the second output command value D2 may correspond to a maximum opening degree of the relief valve 162. The minimum value D20 of the second output command value D2 may correspond to closure of the relief valve 162. The intermediate value D21 of the second output command value D2 may correspond to an intermediate opening degree of the relief valve 162. Between the set of the command controlled variable D and the second output command value D2, the relationship between the command controlled variable D and the second output command value D2 is defined by the linear interpolation.

As shown in FIG. 6, in a case where the command controlled variable D is between the minimum value d0 and the first value d1, the second output command value D2 is between the maximum value D22 and the minimum value D20, and the second output command value D2 has a linear or proportional relationship with the command controlled variable D. In a case where the command controlled variable D is between the first value d1 and the second value d2, the second output command value D2 takes the minimum value D20. Ina case where the command controlled variable D is between the second value d2 and third value d3, the second output command value D2 is between the intermediate value D21 and the minimum value D20, and the second output command value D2 has a linear or proportional relationship with the command controlled variable D. In a case where the command controlled variable D is between the third value d3 and the fourth value d4, the second output command value D2 takes the minimum value D20.

According to the relationship between the command controlled variable D and the second output command value D2, in the output distribution table 181, a discharge flow rate of the compressor body 140 is associated with the opening degree of the relief valve 162 (that is, the flow rate of the bypass pipe 158). When the target flow rate of the compressor unit is zero, the relief valve 162 has the maximum opening degree, and when the target flow rate increases from zero to the lower limit discharge flow rate, the opening degree of the relief valve 162 gradually decreases. When the target flow rate increases from the lower limit discharge flow rate to the first discharge flow rate, the relief valve 162 is closed. When the target flow rate reaches the first discharge flow rate, the relief valve 162 is opened at an intermediate opening degree. When the target flow rate increases from the first discharge flow rate to the second discharge flow rate, the opening degree of the relief valve 162 gradually decreases. When the target flow rate increases from the second discharge flow rate to the upper limit value, the relief valve 162 is closed. When the target flow rate decreases, the opening degree is changed in the opposite manner.

By referring to the output distribution table 181, the compressor controller 168 determines the inverter command signal E such that the operation frequency takes the second value in a case where the target flow rate is between the first discharge flow rate and the second discharge flow rate. At the same time, the compressor controller 168 determines the relief valve command signal R such that the flow rate of the bypass pipe 158 coincides with the differential flow rate obtained by subtracting the target flow rate from the discharge flow rate of the compressor body 140 obtained according to the inverter command signal.

According to the compressor unit according to the embodiment, since the unused interval of the operation frequency is determined to include the natural frequency ω0 of the compressor structure portion 136, the resonance of the compressor structure portion 136 caused by the operation of the compressor body 140 is not easily generated. In addition, since the inverter command signal E is determined such that the operation frequency takes the second value, the working gas is discharged from the compressor body 140 to the high-pressure pipe 144 at a total flow rate obtained by adding a surplus flow rate (corresponding to the above-described differential flow rate) to the target flow rate. Since the relief valve command signal R is determined such that the flow rate of the bypass pipe 158 corresponds to the surplus flow rate, the working gas of the surplus flow rate is collected from the high-pressure pipe 144 to the low-pressure pipe 142. Accordingly, the compressor units 102 and 104 can supply the working gas to the cryocooler 12 at the target flow rate. It is possible to secure a required discharge flow rate while preventing or reducing the resonance which may occur in the inverter-driven compressor unit for the cryocooler without requiring a structural design change.

In addition, in a case where the target flow rate is between the first discharge flow rate and the second discharge flow rate, instead of fixing the operation frequency to the second value, the inverter command signal E may be determined such that the operation frequency is set to be in the second operation frequency interval. In this case, since the operation frequency takes a value larger than the second value, the discharge flow rate of the compressor body 140 increases. By increasing the opening degree of the relief valve 162 and increasing the flow rate of the bypass pipe 158, it is possible to offset the surplus flow rate. However, since the power consumption can be reduced as the operation frequency decreases, it is preferable to set the operation frequency to the second value as described above.

In addition, by referring to the output distribution table 181, the compressor controller 168 determines the inverter command signal E such that the operation frequency is set to be in the first operation frequency interval in the case where the target flow rate is between the lower limit discharge flow rate and the first discharge flow rate. At the same time, the compressor controller 168 determines the relief valve command signal R such that the relief valve 162 is closed. In this case, only the compressor inverter 170 controls the discharge flow rate of the compressor unit. The relief valve 162 is not used so as to control the discharge flow.

In a case where the target flow rate is between the second discharge flow rate and the upper limit discharge flow rate, the compressor controller 168 determines the inverter command signal E such that the operation frequency is set to be in the second operation frequency interval. At the same time, the compressor controller 168 determines the relief valve command signal R such that the relief valve 162 is closed. In this case, only the compressor inverter 170 controls the discharge flow rate of the compressor unit. The relief valve 162 is not used so as to control the discharge flow.

In a case where the target flow rate is between zero and the lower limit discharge flow rate, the compressor controller 168 determine the inverter command signal E such that the operation frequency takes the lower limit value. At the same time, the compressor controller 168 determines the relief valve command signal R such that the flow rate of the bypass pipe 158 coincides with the above-described differential flow rate. In this case, only the relief valve 162 controls the discharge flow rate of the compressor unit.

The compressor controller may perform a smoothing process on the relief valve command signal R and/or the inverter command signal E when the operation frequency is switched from the first value to the second value. For example, the smoothing process may adopt a low-pass filter or temporal smoothing such as moving average, or any other known smoothing process. In this way, it is possible to prevent or reduce adverse effects on a helium gas flow rate caused by a discontinuous change of the relief valve command signal R and/or the inverter command signal E.

It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.

In an embodiment, the CP controller 100 may control the compressor units 102 and 104. The CP controller 100 may include the compressor controller 168. The CP controller 100 may include the compressor inverter 170. The CP controller 100 may include at least one of the relief valve driver 174, the controlled variable calculation unit 176, the deviation calculation unit 178, the output distribution processing unit 180, the output distribution table 181, the inverter command unit 182, and the relief valve command unit 184.

The present invention can be used in fields of a compressor unit for a cryocooler and a cryopump system. 

What is claimed is:
 1. A compressor unit for a cryocooler, comprising: a compressor structure portion which includes a compressor body configured to compress a working gas and discharge the working gas into the cryocooler, a compressor motor which has a variable operation frequency and is configured to operate the compressor body, a high-pressure pipe which is connected to the compressor body such that the working gas is discharged from the compressor body through the high-pressure pipe, a low-pressure pipe which is connected to the compressor body such that the working gas is sucked into the compressor body through the low-pressure pipe, a bypass pipe which bypasses the compressor body and connects the high-pressure pipe to the low-pressure pipe, which allows working gas to flow from the high-pressure pipe to the low-pressure pipe bypassing the compressor body, and a flow control valve which is provided in the bypass pipe to control a flow rate of the bypass pipe according to a valve command signal; a compressor inverter configured to control an operation frequency of the compressor motor according to an inverter command signal; and a compressor controller configured to generate the valve command signal and the inverter command signal such that the working gas is supplied from the compressor unit to the cryocooler at a target flow rate, wherein a range of operation frequency values is limited to a first operation frequency interval from a lower limit value larger than zero to a first value and a second operation frequency interval from a second value to an upper limit value, wherein the second value is larger than the first value, wherein the first value and the second value are defined such that a frequency interval from the first value to the second value includes at least one natural frequency for at least a portion of the compressor structure portion, and wherein the lower limit value, the first value, the second value, and the upper limit value of the operation frequency correspond to a lower limit discharge flow rate, a first discharge flow rate, a second discharge flow rate, and an upper limit discharge flow rate of the compressor body, respectively, and wherein, in a case where the target flow rate is between the first discharge flow rate and the second discharge flow rate, the compressor controller generates the inverter command signal such that the operation frequency is set to be in the second operation frequency interval, and generates the valve command signal such that the flow rate of the bypass pipe coincides with a differential flow rate obtained by subtracting the target flow rate from a discharge flow rate of the compressor body obtained according to the inverter command signal.
 2. The compressor unit according to claim 1, wherein, in the case where the target flow rate is between the first discharge flow rate and the second discharge flow rate, the compressor controller generates the inverter command signal such that the operation frequency is the second value.
 3. The compressor unit according to claim 1, wherein, in a case where the target flow rate is between the lower limit discharge flow rate and the first discharge flow rate, the compressor controller generates the inverter command signal such that the operation frequency is set to be in the first operation frequency interval and generates the valve command signal such that the flow control valve is closed, and wherein, in a case where the target flow rate is between the second discharge flow rate and the upper limit discharge flow rate, the compressor controller generates the inverter command signal such that the operation frequency is set to be in the second operation frequency interval and determines the valve command signal such that the flow control valve is closed.
 4. The compressor unit according to claim 1, wherein, in a case where the target flow rate is between zero and the lower limit discharge flow rate, the compressor controller generates the inverter command signal such that the operation frequency is the lower limit value, and generates the valve command signal such that the flow rate of the bypass pipe coincides with the differential flow rate.
 5. The compressor unit according to claim 1, wherein the compressor controller performs a smoothing process on the valve command signal or the inverter command signal when the operation frequency is switched from the first value to the second value.
 6. A cryopump system comprising: a cryopump which includes a cryopanel and a cryocooler configured to cool the cryopanel; a compressor unit having a compressor structure portion including a compressor body configured to compress a working gas and discharge the working gas into the cryocooler, a compressor motor which has a variable operation frequency and is configured to operate the compressor body, a high-pressure pipe which is connected to the compressor body such that the working gas is discharged from the compressor body though the high-pressure pipe, a low-pressure pipe which is connected to the compressor body such that the working gas is sucked into the compressor body through the low-pressure pipe, a bypass pipe which bypasses the compressor body and connects the high-pressure pipe to the low-pressure pipe, which allows working gas to flow from the high-pressure pipe to the low-pressure pipe bypassing the compressor body, and a flow control valve which is provided in the bypass pipe to control a flow rate of the bypass pipe according to a valve command signal; a compressor inverter configured to control an operation frequency of the compressor motor according to an inverter command signal; and a controller configured to generate the valve command signal and the inverter command signal such that the working gas is supplied from the compressor unit to the cryocooler at a target flow rate, wherein a range of operation frequency values is limited to a first operation frequency interval from a lower limit value larger than zero to a first value and a second operation frequency interval from a second value to an upper limit value, wherein the second value is larger than the first value, wherein the first value and the second value are defined such that a frequency interval from the first value to the second value includes at least one natural frequency for at least a portion of the compressor structure portion, and wherein the lower limit value, the first value, the second value, and the upper limit value of the operation frequency correspond to a lower limit discharge flow rate, a first discharge flow rate, a second discharge flow rate, and an upper limit discharge flow rate of the compressor body, respectively, and wherein, in a case where the target flow rate is between the first discharge flow rate and the second discharge flow rate, the controller generates the inverter command signal such that the operation frequency is set to be in the second operation frequency interval, and generates the valve command signal such that the flow rate of the bypass pipe coincides with a differential flow rate obtained by subtracting the target flow rate from a discharge flow rate of the compressor body obtained according to the inverter command signal. 